whole-marsden-smedley-thesis.pdf (6.61 MB)
Fire and fuel in Tasmanian buttongrass moorlands : regimes, characteristics, behaviour and management
thesisposted on 2023-05-26, 01:50 authored by Jonathan Marsden-SmedleyJonathan Marsden-Smedley
The aims of this thesis are to examine the fire regimes, fuel characteristics, fire behaviour and fire management of Tasmanian buttongrass moorlands. Major changes have occurred to the fire regime of southwest Tasmania over the past 170 years. The fire regime has changed from an Aboriginal regime of mostly frequent low intensity buttongrass moorland fires to the early European fire regime of frequent high intensity fires in all vegetation types, to a regime of low to medium intensity buttongrass moorland fires and finally to the current regime of very few fires. Buttongrass moorland fuel accumulation rates in western and southwestern Tasmania can be divided into two productivity groups, based on geological type. Within each productivity group, the vegetation cover and/or the time since the last fire can be used to model fuel load and the dead fuel load. Dead fuel moistures in buttongrass moorlands can be predicted from the relative humidity and dew point temperature. The main influences on buttongrass moorland rates of fire spread are wind speed, dead fuel moisture and age. Flame height in these moorlands is highly correlated with the fuel consumption rate, which in tum is controlled by the rate of fire spread, fuel load and dead fuel moisture. Operational fire behaviour models have been developed which use the wind speed, temperature, relative humidity, age and site productivity to predict the frre spread rate and flame height. The prescriptions for burning buttongrass moorlands have also been refined. Wildland fire management is a major problem in western and southwestern Tasmania. This is mainly due to the extensive area of fire-adapted and fire-dependent vegetation, the small area burnt by natural fires, the high incidence of arson in some areas and across much of the region, the old-growth nature of the buttongrass moorland vegetation. If we are going to preserve the ecological values of the region whilst minimising the economic and social costs of management, we are going to have to reintroduce frre into the region. Such reintroductions of fire will need to be performed in a highly sophisticated manner in order to maximise the potential that they will achieve the desired outcomes.
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